El universo :

1. El universo: Edad: 13.7 millardos de años (1 % de error) Expansión: 71 km/sec/Mpc actualmente (5 % de error) 73% = Energía oscura 23% = materia oscura fría 4% = átomos de materia ordinaria Ocurrió una etapa de expansión rápida (inflación) Se expandirá para siempre.

2. The Galaxies We assume the stars are grouped together into galaxies and that these form the basic building blocks of the visible matter in the Universe. • The image shows the Hubble Deep Field: the Hubble Space Telescope was pointed at the same region of the sky (in the constellation Ursa Major) for 10 days and images were combined to give the most distant optical view of the Universe. Almost every object is a galaxy, and objects down to visual magnitude +30 can be seen.

3. Classification of Galaxies • Using a system proposed by Edwin Hubble (1926 & 1936), astronomers classify galaxies into three major types: • Spiral (~75%) • Elliptical (20%) • Irregular (5%) • The sizes of all three types span a wide range, from • dwarf galaxies • which contain 100 million (108) stars • to • giant galaxies • which contain 1 trillion (1012) stars

4. The Hubble Classification

9. Spiral Galaxies • have a disk component and bulge & halo (spheroidal component) • diskcontains an ISM of gas & dust • relative sizes of bulge/disk & amount of ISM vary among galaxies • contain both blue & red stars

10. Spiral Galaxies Properties: Mass: 109 - 1012 M⊙ Diameter: 5 - 50 kpc Luminosity: 108 - 1011 L⊙ Structure & Dynamics: Disk + Spheroid Supported by relatively rapid rotation, but in the spheroid - random motions. ~10-20% gas On-going star formation in the disks Mix of Pop I and Pop II stars NGC 1232 is located in the constellation Eridanus . The distance is about 100 million light-years. The central areas contain older stars of red color, while the spiral arms are populated by young, blue stars and many star-forming regions.

11. Some spiral galaxies have a bar of stars cutting through their centers. spiral arms are attached to the ends of the bar we call them barred spiral galaxies. Some galaxies have disks with no spiral arms. we call then lenticular galaxies they look like a lens seen edge-on They contain less cool gas than normal spirals. Barred Spiral Galaxies

12. Elliptical Galaxies • only have a spheroidal component;nodisk component • very little ISM, which is mostly low-density and ionized. • contain mostly red stars

13. Elliptical Galaxies Properties: Mass: 105 - 1013 M⊙ Diameter: 1 - 200 kpc Luminosity: 106 - 1012 L⊙ Structure & Dynamics: • Spheroid of old stars with little gas or dust • Supported by random motions of stars with some very slow rotation • Very little or no gas or dust • Star formation ended billions of years ago • See only old Pop II stars

14. Irregular Galaxies • “none of the above” category; neither spiral nor elliptical • appear white & dusty with ISM • have more in common with the disk component of spirals • distant galaxies are more likely to be irregular • they were more common when the Universe was young

15. Irregular Galaxies Properties: Mass: 106 - 1011 M⊙ Diameter: 1 - 10 kpc Luminosity: 106 - few x 109 L⊙ Irregulars: • Can range up to 90% gas • On-going star formation • Dominated by young Pop I stars • Dwarf Irregulars: • Very metal poor (<1% solar) • Forming stars for the first time only now. Structure & Dynamics: Chaotic structure, lots of young blue stars Moderate rotation in Irregulars, but very chaotic motions as well.

16. Among large galaxies… most (75–85%) are spirals they tend to associate in loose groups of several galaxies Some galaxies are associate in clusters. contain hundreds of galaxies Groups and Clusters of Galaxies • Our Local Group (at least 40) is an example. • dominated by two large spirals • the Milky Way • Andromeda

17. LMC • The Large Magellanic Cloud is one of the closest galaxies – 50 kpc. The Sagitarrius dwarf is at 24 kpc. • It is of fundamental importance for: - studies of stellar populations - interstellar medium - dark objects in the Galactic Halo through microlensing - determinations of the extragalactic distance scale

18. LMC Morphologically: • In the optical wavelength is dominated by the bar, regions of strong star formation, and dust absorption. - in the near IR is more uniform, hint of some spiral structure (de Vaucouleurs & Freeman 1973), but with very low contrast. • The LMC is generally considered an irregular galaxy as a result of these characteristics. It is in fact the prototype of the class of galaxies called “Magellanic Irregulars'' (de Vaucouleurs & Freeman 1973).

19. LMC The kinematical properties: • Gas – HI maps (Kim et al 1998). • From discrete LMC tracers: (Gyuk, Dalal & Griest 2000). A common result from all these studies is that the line-of-sight velocity dispersion of the tracers is at least a factor of 2 smaller than their rotation velocity. This implies that the LMC is kinematically cold, and must therefore be a disk system.

20. SMC • The Small Magellanic Cloud (SMC) dwarf galaxy is a satellite galaxy of our Milky Way. • It contains numerous emission nebulae, which are clouds of gas that glow red as the hydrogen gas they contain is ionised by radiation from nearby hot young stars. • The SMC lies about 185,000 light year from Earth, in the constellation Tucana.

21. Regions of the Milky Way Galaxy • The Milky Way Galaxy consists of a thin disk about 100,000 light-years in diameter with a central bulge. • The spherical region surrounding the entire disk is called the halo. Sun is in disk, 28,000 l.y. out from center

22. Regions of the Milky Way Galaxy • Disk • younger generation of stars • contains gas and dust • location of the open clusters • Bulge • mixture of both young and old stars • Halo • older generation of stars • contains no gas or dust • location of the globular clusters